Mystic Journey must pass a crucial distance test in the Group One Turnbull Stakes to keep the Cox Plate dream alive.

But trainer Adam Trinder is confident the star Tasmanian mare and equal Cox Plate favourite will do just that at Flemington on Saturday.

"She's trained right on from the Makybe Diva Stakes and she's going to go there tomorrow and run a really forward race for us, I trust," Trinder said.

Mystic Journey runs over 2000m for the first time in the Turnbull, for which she is favourite, and from a Cox Plate perspective Trinder needs to see her perform strongly to be pressing ahead with confidence to the $5 million 2040m race at The Valley later this month which is the mare's major target.

"Obviously if she doesn't run a strong 2000 metres tomorrow she won't be at the Cox Plate in three weeks time. We'll re-assess," Trinder said.

"Obviously we're really confident that she will run the 2000 metres.

"So just to see her hitting the line with good enthusiasm - win, lose or draw.

"Flemington 2000 metres in comparison to Moonee Valley 2000 metres is two totally different scenarios but you've still got to run the journey on the day so we'll get a really accurate assessment moving forward to a Cox Plate tomorrow."

Trinder says Mystic Journey has been strong through the line in each of her 15 starts, which has netted 11 wins, and is convinced she will give herself every opportunity to excel at the distance.

"She will drop her head, relax and breathe and build. So I don't see it as a problem," he said.

Mystic Journey was beaten for the first time in a year in the Group One Makybe Diva Stakes (1600m) last start on September 14, finishing second to Gatting but Trinder lost no admiration or confidence in his stable star.

"We thought it was a fantastic performance," he said.

"She actually ran a personal best, time-wise.

"They went a lot quicker there than what they did in her Guineas win or in her All-Star Mile win over the mile at Flemington.

"She was just beaten by a better horse on the day.

"But our filly was very brave in defeat and we lost no admiration for her that's for sure."

The former star jumps jockey turned trainer has been thrilled with Mystic Journey's progression since, saying her recent work had been outstanding.

Mystic Journey was $2.70 for the Turnbull on Friday while she shares Cox Plate favouritism at $5 with Avilius.

Trinder, whose grandfather Ray owned 1972 Melbourne Cup winner Piping Lane, says having a contender in the time-honoured Cox Plate would mean a lot and be a massive achievement.

"My grandfather won a Melbourne Cup in 1972 so the family has been fortunate enough to win one of the holy grail races," he said.

"So if we could get our opportunity in a Cox Plate that would be the highlight of my career by far."